1. Field of the Invention
This invention relates to molecular sieve bed containers and is more particularly concerned with the form and construction of molecular sieve bed containers for gas separation apparatus.
2. Description of the Prior Art
It is current practice in molecular sieve type gas separation apparatus and systems having multiple sieve beds for each sieve bed to be provided in an individual container. Examples of such systems, which are particularly suited for the production of oxygen-enriched air for breathing by aircrew in an aircraft application, are disclosed in EP-A-0,080,300 and EP-A-0,129,304 (Normalair-Garrett). However, as with all ancillary equipment required to be carried by an aircraft, it is of great advantage for molecular sieve beds to be of minimum size and weight compatible with required performance and physical integrity.
GB-A-2,013,101 (Bendix) discloses apparatus for producing oxygen-enriched air wherein pressurised air is passed through a molecular sieve bed which removes nitrogen from the supply air and through which a portion of the oxygen-enriched product gas is passed as a purge gas for regenerating the molecular sieve material. The sieve bed is defined by a housing or container which provides a larger flow area at the inlet face of the bed than at the outlet face thereof.
In one disclosed embodiment a sieve bed is formed by an annular portion having one flow area disposed around a tubular core of a lesser flow area and arranged so that flow through the bed reverses its direction under an end cap at one end of the container in passing from the annular part to the tubular core. In another disclosed embodiment of simpler form the sieve bed is of a frusto-conical shape having a single pass flow-path from an inlet end of one flow area to an outlet end of a smaller flow area.
Thus, GB-A-2,013,101 is concerned to provide a container for an individual molecular sieve bed which matches velocity of product gas output from the sieve bed with that of supply gas input to the sieve bed thereby compensating for the gas element of the supply gas which is adsorbed by the molecular sieve material.